Wind Turbine Noise: What does the new draft replacement for ETSU-R-97 mean for developers?
The UK Government has released a new draft guidance to replace the extant ETSU-R-97 The Assessment and Rating of Wind Turbine Noise, bringing it into line with modern turbine design, scientific understanding, and planning policy.
As specialists in wind turbine noise for over 15 years, the team at Metrica have seen how even small changes to guidance can have unintended consequences for developers. So, what are the key changes? Will it add further constraints to wind farm design? Here’s what you need to know:
Firstly, and most importantly, the Government is clear that… “this draft guidance update does not represent a final position from government” and “planning authorities should continue to use existing guidance”. The content of the draft does not affect the assessment methodology stipulated in EN-3 (i.e. ETSU-R-97 and the Institute of Acoustic’s Good Practice Guide (‘the GPG’)).
As for the draft changes themselves, the key points are as follows:
🔷 An increase in the ‘simplified assessment’ criterion from 35 dB(A) to 37 dB(A). This means that providing maximum noise levels are below 37 dB(A), a proposed wind farm would be acceptable without the need to consider background noise levels. This will reduce the geographical scale of cumulative assessments, and mean that background noise surveys will be required less often.
🔷 If a background noise survey is required, the survey is conducted in the same way as currently (i.e. in line with the GPG). The difference is that the daytime and night-time limits are then combined to provide a single set of limits which applies at all times. Whilst this will have some effect on night-time noise curtailment, it is unlikely to substantially more restrictive in practice.
🔷 Additional clarity is provided with regard to determining the appropriate fixed lower limit (or ‘lower limiting value’) and the assessment of cumulative effects. There are number of small technical changes, but the general principles remain the same. In Metrica’s opinion, based on our substantial prior experience, these changes do not materially change the current state of play in terms of the feasibility of new wind farms in existing cumulative environments.
🔷 Confirmation that tonality and elevated amplitude modulation (AM) cannot be assessed at the planning stage, and are best controlled through the application of appropriate planning conditions. This results in no changes in practical terms to the current approach.
💡 In summary:
The draft provides welcome additional clarity, bringing the guidance more in line with wider government planning policy. It provides pragmatic recommendations to allow for the growth of appropriate wind farm development, whilst protecting the amenity of local communities.
We are aware that there has been some trepidation by developers regarding what the proposed changes will entail, but we hope the above will settle a few nerves. If you have any questions, or are considering a new wind farm development, we would be happy to help! Please get in touch with us at www.metricaconsulting.co.uk or info@metricaconsulting.co.uk.
